Raspberry Pi's Raspbian OS Finally Spins 64-bit Version

[mangeek]

I'm really curious how they pulled off the magic to get the guest OS to be 64 bits when the host was just 32. There's got to be a lot of painful kludging going on there.!

The hardware and 64-bit OS are totally native. There's actually less 'kludging' going on with 64-bit on these things than 32-bit.

[willmore]

I'm guessing it's the way it does on x86 PAE, or in ARM's nomenclature LPAE, Large Physical Address Extension. Extends the physical address space from 32 bits to 40 bits or 44 bits depending on the ARM CPU. I'd imagine addressing RAM beyond a 32 bit space would require extra CPU cycles with a 32 bit OS so having a properly 64 bit clean and optimized kernel and user space would likely save on RAM addressing cycles alone. If it's anything like PAE it's just a way of bringing segmented memory architecture forward to reach above the 32 bit 4GB address limit. I'm not that familiar with ARM's family tree, however, so I'm guessing on how LPAE is architected.

If you're interested, look up Physical Address Extension and segmented memory to learn more.

Page tables map virtual addresses to physical ones. LPAE lets those physical addresses be larger than 32 bits. Pointers in user and kernel space are always *virtual*, so they have to get translated to physical addresses. For user space, there is no difference. For the kernel, there's a lot more pain because you can't just use a pointer to address all of memory, you have to go through extra steps. Maybe that's what you mean by "extra CPU cycles". User space doesn't (have to do extra work) as a pointer always had to get translated through a page table to a physical address. The Kernel used to just have one entry that said "virtual addresses map 1:1 to physical addresses" and went about life thinking that was true. So implementing PAE/LPAE took some doing. Fortunately, that happened on the Intel side with the Pentium Pro, so the support for it is very old and solid. So, by the time LPAE came around in the ARM world, adding it wasn't a big deal--all the heavy lifting had been done years before.

[stormcrow]

Huh? Using a 64-bit kernel, or how does that work?

I'm guessing it's the way it does on x86 PAE, or in ARM's nomenclature LPAE, Large Physical Address Extension. Extends the physical address space from 32 bits to 40 bits or 44 bits depending on the ARM CPU. I'd imagine addressing RAM beyond a 32 bit space would require extra CPU cycles with a 32 bit OS so having a properly 64 bit clean and optimized kernel and user space would likely save on RAM addressing cycles alone. If it's anything like PAE it's just a way of bringing segmented memory architecture forward to reach above the 32 bit 4GB address limit. I'm not that familiar with ARM's family tree, however, so I'm guessing on how LPAE is architected.

If you're interested, look up Physical Address Extension and segmented memory to learn more.

[Quackdoc]

Why wouldn't it? RPi has been a common platform for watching stolen movies with OpenELEC since 2012.

It may be a small ship, but a small ship was fine for jack sparrow it'd be fine for me as well

[coder]

I use 32-bit RPi OS with the 8 GiB model and I'll probably stick with it unless there is an obvious performance benefit.

Huh? Using a 64-bit kernel, or how does that work?

[coder]

Didn't they make a big fuss, ~2 years ago, about how they're switching from "Raspbian" to "Raspberry Pi OS". I realize that page linked by the article still says Raspbian, in a few places, but a lot more mentions of "Raspberry Pi OS".

One thing I didn't like about Raspbian was how much it sounded like Rasputin.

[caligula]

Is video decoding in hardware (h.264 & h.265) working now?

Why wouldn't it? RPi has been a common platform for watching stolen movies with OpenELEC since 2012.

[andrebrait]

Is video decoding in hardware (h.264 & h.265) working now?

IIRC yes, but you have to use the following in your config.txt:

dtoverlay=vc4-kms-v3d,cma-512
dtoverlay=rpivid-v4l2

[dremon_nl]

I've been using openSUSE MicroOS 64-bit on my RPi4 for quite some time already, with cockpit and podman containers. Works great.

[jaxa]

I use 32-bit RPi OS with the 8 GiB model and I'll probably stick with it unless there is an obvious performance benefit.

Is video decoding in hardware (h.264 & h.265) working now?

Hahah